Abstract
To study the influence of different cooling methods on dynamic mechanical properties of high temperature rock, both natural cooling and water cooling were used to cool high temperature (100°C∼1000°C) coal mine sandstone to room temperature (20°C). Basic physical parameters of sandstone were measured, and impact compression tests were carried out by using the SHPB test device. Comparative analysis shows that the volume expansion rate, mass loss rate, density reduction rate, and P-wave velocity reduction rate of sandstone specimens are positively correlated with the temperature in a quadratic function. The deteriorate rate of physical parameters of water cooling sandstone specimens is slightly larger than that of natural cooling. The variation of dynamic stress-strain curves is basically consistent. Compaction stage of water cooling is slightly larger than that of natural cooling. With the increase in temperature, dynamic compressive strength of sandstone specimens first increases, then decreases, and reaches maximum at 300°C. Subsequently, dynamic compressive strength decreases in a quadratic function with the temperature, and dynamic compressive strength of water cooling sandstone specimens is significantly lower than that of natural cooling. The dynamic elastic modulus also first increases and then decreases with the temperature and reaches maximum at 300°C. The dynamic elastic modulus of water cooling sandstone specimens is lower than that of natural cooling, but they are roughly the same at 1000°C. Dynamic strain increases in a quadratic function with the temperature, and dynamic strain of water cooling sandstone specimens is greater than that of natural cooling. The impact failure of sandstone specimens is intensified with the temperature, and the failure degree of water cooling is greater than that of natural cooling.
Highlights
Rock often experiences long-term high temperature heating and rapid cooling in geotechnical engineering and other fields
According to test methods recommended by the International Society of Rock Mechanics (ISRM) [30], sandstone specimens were processed into cylinder with the size of φ50 mm × 25 mm, and the aspect ratio is 0.5 to meet the requirements of stress equilibrium and inertial effect in the SHPB test
Figures 3∼5 are the deteriorate rates of volume, mass, and density of high temperature sandstone specimens after two cooling methods
Summary
Rock often experiences long-term high temperature heating and rapid cooling in geotechnical engineering and other fields. Modern tunnels and underground caverns may encounter fire and explosion accidents, and the rock walls of tunnels and caverns may experience fire extinguishing and water cooling after long-term high temperature heating. Erefore, studying the physical and mechanical properties of rock after different high temperature treatments has significance for the safe production and disaster prevention. Some scholars have conducted experimental studies on static and dynamic mechanics of rock under and after high temperature. Sirdesai et al [3] conducted high temperature heating of fine-grained red sandstone at 50°C∼500°C for 5, 10, 15, 20, and 30 days and studied the effects of thermal treatment duration on the physical properties and tensile strength of red sandstone. Yang et al [4] conducted the Brazilian splitting test and conventional triaxial compression
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